Pakistani troops launched a major operation against militants who stormed a police academy in the country's restive southwest in an attack that left at least one official dead and 84 wounded as it continued into early Tuesday.

The attack on the Balochistan Police College, located 20 kilometres east of Quetta city centre, began at around 11:30 pm (1830 GMT) Monday, with gunfire continuing to ring out from the site hours later.

According to a military statement "five to six" militants were involved, with a clearing operation beginning shortly after.

Provincial secretary health Noor-ul-Haq Baloch told AFP "an injured police official died on his way to a local hospital from the attack site" and the number of injured had risen to 84, ten of whom had major gun shot or bomb-related injuries.

Mir Sarfaraz Ahmed Bugti, the provincial home minister, had earlier tweeted "2 terrorist killed" and "200 plus rescued Alhamdo lillha (by God's grace)".

It was not immediately clear how many cadets were in the building at the time of the attack. Bugti said it normally housed around 700 but "recently there was a batch which graduated so I can't say how many there are now".

As the battle to retake the academy continued, police and civil administration officials at the site told AFP they had heard several loud blasts.

The area was plunged into darkness when the operation was launched while security personnel created a cordon and ambulances zoomed in and out, taking the injured to hospitals. Military helicopters meanwhile circled overhead.

A man who identified himself as a police cadet told reporters: "I saw three men in camouflage whose faces were hidden carrying Kalashnikovs. They started firing and entered the dormitory but I managed to escape over a wall."


Unclear motive

No group has yet claimed responsibility but Baloch separatists demanding greater autonomy of the mineral rich but desperately poor region have been waging an on-off insurgency for decades, and the province is also riven by sectarian strife and Islamist violence.

The attack came a day after separatist gunmen for the Baloch Liberation Army on a motorcycle shot dead two coast guards and a civilian and wounded a shopkeeper in a remote southwest coastal town in the same province.

In August, a suicide bombing at a Quetta hospital claimed by the Islamic State group and the Jamaat-ul-Ahrar faction of the Pakistani Taliban killed 73 people, including many of the city's lawyer community who had gone there to mourn the fatal shooting of a colleague.

Balochistan is also a key region for China's ambitious $46 billion China-Pakistan Economic Corridor (CPEC) infrastructure project linking its western province of Xinjiang to the Arabian Sea via Pakistan.

Security problems have mired CPEC in the past with numerous separatist attacks, but China has said it is confident the Pakistani military is in control.

The army has repeatedly been accused by international rights groups of abuses in Balochistan.